Borrowed Time: The Science of How and Why We Age

by Sue Armstrong

There were hints in the literature that perhaps senescent cells had some positive attributes, too, and so Campisi and her colleagues took a closer look at them. They found that as well as collagen-chewing molecules and inflammatory cytokines, the secretory substances also include growth factors – molecules that encourage repair and regeneration of tissue. They already knew that in order to heal a wound, our bodies need to mount an inflammatory response (that's why, when you cut yourself, the flesh around the cut goes pink and hot for a while). To test a hunch that maybe senescent cells are actively involved in wound healing, Campisi's team created a transgenic mouse in which these cells expressed a protein that made them glow so they were easily identifiable among other cells in the body. They then made small wounds on the backs of their lab mice and found that, sure enough, senescent cells were clustered at the site of the wounds. When they eliminated the senescent cells, the wounds were very much slower to heal.